Which answer correctly identifies a unique characteristic or behavior of a flatfish?

Flatfish have a unique characteristic that is present in all species- both eyes lie on one side of the head, one or the other migrating through or around the head during development. Some species face their left sides upward, some face their right side upward, and others face either side upward.

Other distinguishing features of the flatfish are the presence of protrusible eyes, another adaptation to living on the seabed.

From a taxonomical perspective, there are over 800 described species that are placed into 16 families.

The flatfish is found in oceans worldwide, ranging from the Arctic, through the tropics, to Antarctica.

In 2008, a 50-million-year-old fossil ‘Amphistium’ was identified as an early relative of the flatfish and is considered a transitional fossil. While the typical modern flatfish has a head that is asymmetric, with both eyes on one side of the head, in ‘Amphistium’, the transition from the typical symmetric head of a vertebrate is incomplete, with one eye placed near the top of the head.

Based on this finding, researchers concluded, “the change happened gradually, in a way consistent with evolution via natural selection- not suddenly, as researchers once had little choice but to believe”.

As a food source, the flatfish have a high concentration of oils with its liver offering a unique flavor that differs from species to species. Methods of preparing flatfish include grilling, pan-frying, baking and deep-frying.